In endodontic treatment, precise measurement control is one of the basic tenants. Canal length is determined by several techniques, the most common being the interpolation of an X-ray of the tooth with an endodontic instrument of known length in place. Another technique involves the use of electrical measuring devices. The endodontic literature has numerous studies that show the reliability of these techniques to be at best 95%.
This limited reliability creates the possibility that the dental practitioner may be misinformed about the exact length of the canal. Current techniques of endodontic treatment strive to have the narrowest point of the canal preparation to be at the apical terminus. This is referred to as the apical constriction. However, as current canal length determination technology provides a less than ideal margin of error. A means of exact determination of the location of the constriction would be a great aid.